Uplink control channel for low latency communications

ABSTRACT

Methods, systems, and devices for wireless communication are described. A wireless device such as a user equipment (UE) or a base station may identify a set of resource element groups (REGs) for low latency communication, and each REG may include a portion of a different resource block (RB) of a set of RBs (e.g., a set of non-contiguous RBs). The device may then map an uplink control channel to the selected REGs and communicate on the uplink control channel accordingly. Reference signals may also be transmitted in the same RBs, and the REGs may be mapped around the resources used for reference signals. In some cases, multiple UEs may transmit uplink control data using the same resources using code division multiplexing (CDM) (e.g., if the control payload is relatively small). In other cases, multiple UEs may be frequency division multiplexed (FDM).

CROSS REFERENCES

The present application for Patent claims priority to U.S. ProvisionalPatent Application No. 62/241,997 entitled “UPLINK CONTROL CHANNEL FORLOW LATENCY COMMUNICATIONS,” filed Oct. 15, 2015, assigned to theassignee hereof.

BACKGROUND

The following relates generally to wireless communication and morespecifically to uplink control channel configurations for low latencycommunications.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems. A wireless multiple-accesscommunications system may include a number of base stations, eachsimultaneously supporting communication for multiple communicationdevices, which may be otherwise known as user equipment (UE).

Wireless multiple-access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis Long Term Evolution (LTE). LTE is designed to improve spectralefficiency, lower costs, improve services, make use of new spectrum, andbetter integrate with other open standards. LTE may use OFDMA on thedownlink (DL), single-carrier frequency division multiple access(SC-FDMA) on the uplink (UL), and multiple-input multiple-output (MIMO)antenna technology.

In some cases, a wireless system may support low latency operationsusing subframes, symbol periods, or transmission time intervals (TTI) ofdifferent durations. Low latency communication may use communicationtechniques and formats that are similar to non-low latencycommunications. Low latency uplink control transmissions based on anon-low latency configuration may, however, result in inefficientmanagement of wireless resources and increased implementation andoperation costs.

SUMMARY

A wireless device such as a user equipment (UE) or a base station mayidentify a set of resource element groups (REGs) for low latencycommunication. Each REG of the set may include a portion of a differentresource block (RB) of a set of RBs (e.g., a set of RBs that arenon-contiguous in the frequency domain). The device may then map anuplink control channel to the selected REGs and communicate on theuplink control channel accordingly. Reference signals may also betransmitted in the same RBs, and the REGs may be mapped around theresources used for reference signals. In some cases, multiple UEs maytransmit uplink control data using the same resources using codedivision multiplexing (CDM) (e.g., if the control payload is relativelysmall). In other cases, multiple UEs may be frequency divisionmultiplexed (FDM), such that different UEs may transmit uplink controldata using resources of different resources (e.g., differentsubcarriers) in the frequency domain.

A method of wireless communication is described. The method may includeidentifying a set of REGs, wherein each REG of the set of REGs comprisesa portion of a respective RB of a set of RBs. The method may alsoinclude mapping an uplink control channel for a wireless communicationlink to the set of REGs and communicating on the uplink control channelusing the set of REGs.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying a set of REGs, wherein each REG of the setof REGs comprises a portion of a respective RB of a set of RBs. Theapparatus may also include means for mapping an uplink control channelfor a wireless communication link to the set of REGs, and means forcommunicating on the uplink control channel using the set of REGs.

Another apparatus is described. The apparatus may include a processor,memory in electronic communication with the processor, and instructionsstored in the memory. The instructions may be operable to cause theprocessor to identify a set of REGs, wherein each REG of the set of REGscomprises a portion of a respective RB of a set of RBs. The instructionsmay also be operable to cause the processor to map an uplink controlchannel for a wireless communication link to the set of REGs, andcommunicate on the uplink control channel using the set of REGs.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions to cause a processor to identify a set of REGs, where eachREG of the set of REGs comprises a portion of a respective RB of a setof RBs. The non-transitory computer-readable medium may also includeinstructions to map an uplink control channel for a wirelesscommunication link to the set of REGs, and communicate on the uplinkcontrol channel using the set of REGs.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein may include operations,features, means, or instructions for identifying an offset associatedwith a user equipment (UE); and transmitting an uplink reference signalusing the offset in each RB of the set of RBs. In some examples, theuplink reference signal may be transmitted during symbol periods thatinclude the uplink control channel. In some examples, the uplinkreference signal may be transmitted during symbol periods indicated by abase station. In some examples, the uplink reference signal may beassociated with an uplink control channel, or an uplink shared channel,or both.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein, the set of REGs may besemi-statically configured according to an indication communicated usingradio resource control (RRC) signaling. In some examples of the method,apparatuses, or non-transitory computer-readable medium as describedherein, the set of REGs may be dynamically configured using anindication communicated in a downlink message. In some examples of themethod, apparatuses, or non-transitory computer-readable medium asdescribed herein, the set of RBs may be non-contiguous.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein, a waveform of the uplinkcontrol channel may include an orthogonal frequency divisionmultiplexing (OFDM) waveform, a discrete Fourier transform spread OFDM(DFT-S-OFDM) waveform, or an interleaved frequency division multiplexing(IFDM) waveform.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein may include operations,features, means, or instructions for identifying a code divisionmultiplexing (CDM) cover code, wherein communicating over the wirelesscommunication link is based at least in part on the CDM cover code. Insome examples, the CDM cover code comprises resource elements of two ormore different subcarriers in a frequency domain, or resource elementsof two or more different symbol periods in a time domain, or acombination thereof. Some examples may include operations, features,means, or instructions for determining a payload size of the uplinkcontrol channel, wherein identifying the CDM cover code is based atleast in part on the payload size.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein, each REG of the set ofREGs comprises a set of resource elements (REs) that comprise datainterleaved with REs that comprise a reference signal, wherein theinterleaving comprises alternating one of the REs that comprise datawith one of the REs that comprise the reference signal during a symbolperiod of an RB of the set of RBs.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein, each REG of the set ofREGs comprises a set of REs that comprise data interleaved with REs thatcomprise a reference signal, wherein the interleaving comprisesalternating two of the REs that comprise data with one of the REs thatcomprise the reference signal during a symbol period of an RB of the setof RBs.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein may include operations,features, means, or instructions for identifying a quantity of REGs inthe set of REGs based at least in part on a content of the uplinkcontrol channel.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein, communicating over thewireless communication link may include operations, features, means, orinstructions for transmitting a reference signal and first data in afirst REG of the set of REGs during a first symbol period; andtransmitting second data in each RE of a second REG of the set of REGsduring a second symbol period that follows the first symbol period.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein may include operations,features, means, or instructions for identifying a transmit antenna or atransmit port for each REG of the set of REGs.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein, the communicating mayinclude operations, features, means, or instructions for transmitting asounding reference signal (SRS) during a last symbol period of atransmission time interval that comprises the uplink control channel.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium as described herein may include operations,features, means, or instructions for identifying a first REG structureassociated with a first UE and a second REG structure associated with asecond UE; and receiving a first uplink reference signal from the firstUE using the first REG structure in an RB of the set of RBs. Someexamples may include operations, features, means, or instructions forreceiving a second uplink reference signal from the second UE using thesecond REG structure in another RB of a set of RBs. In some examples thefirst REG structure and the second REG structure differ at least in oneof a frequency offset, a number of REs for reference signals, or a CDMcover, or a combination thereof. Some examples may include operations,features, means, or instructions for receiving data or controlinformation in each RE of an REG associated with the first UE in anotherRB during a second symbol duration, the set of REGs comprising the REGassociated with the first UE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communications system thatsupports uplink control channel configurations for low latencycommunications in accordance with aspects of the present disclosure;

FIG. 2 illustrates an example of a wireless communications system thatsupports uplink control channel configurations for low latencycommunications in accordance with aspects of the present disclosure;

FIGS. 3A, 3B and 3C illustrate examples of uplink control channelconfigurations for low latency communications in accordance with aspectsof the present disclosure;

FIG. 4 illustrates an example of a process flow in a system thatsupports uplink control channel configurations for low latencycommunications in accordance with aspects of the present disclosure;

FIGS. 5 through 7 show block diagrams of a wireless device or devicesthat support uplink control channel configurations for low latencycommunications in accordance with aspects of the present disclosure;

FIG. 8 illustrates a block diagram of a system including a UE thatsupports uplink control channel configurations for low latencycommunications in accordance with aspects of the present disclosure;

FIG. 9 illustrates a block diagram of a system including a base stationthat supports uplink control channel configurations for low latencycommunications in accordance with aspects of the present disclosure; and

FIGS. 10 through 13 illustrate methods for uplink control channelconfigurations for low latency communications in accordance with aspectsof the present disclosure.

DETAILED DESCRIPTION

Some wireless communications systems may use a reduced or variabletransmission time interval (TTI) duration, relative to other TTIdurations used in the system, to reduce latency between downlink (DL)and uplink (UL) transmissions. Low latency communications may becharacterized by shorter latency for hybrid automatic repeat request(HARQ) feedback and retransmissions, for example. Considerationsrelevant to uplink control channels may be different for these lowlatency communications than considerations motivating uplink controlchannel design for other, non-low latency communications. For instance,peak-to-average power ratio (PAPR), which may generally be a motivatingconcern in uplink control channel design, may be less significant in thecontext of low latency communications. Other factors, such as timediversity, spatial diversity, or HARQ payload size may be moresignificant considerations in some low latency deployments.

Multiple devices in systems that support low latency communications maythus communicate on radio frequencies by using an orthogonalfrequency-division multiple access (OFDMA) scheme or non-single-carrierfrequency division multiple access (non-SC-FDMA) for uplink (UL)transmissions. Use of OFDMA or other non-SC-FDMA schemes in the uplinkmay favorably accommodate time diversity, spatial diversity, or payloadconcerns. Low latency communication may coexist with other ULtransmissions (e.g., UL transmissions sent according to differentnumerologies) in the same subframe or symbol period.

Different channel configurations may be used for orthogonal frequencydivision multiplexing (OFDM) UL control channel transmissions depending,for example, on a payload size of an uplink transmission. For example,for relatively small payloads, a first configuration may be associatedwith resource element groups (REGs) that are frequency distributed e.g.,across resource blocks that are non-contiguous in the frequency domain)and may use code division multiplexing (CDM) for multiple UEs. Thisconfiguration may enable transmissions from different UEs to bemultiplexed in the same resource elements (REs). Smaller payloads maythus allow for increased time diversity because control channels ofseveral UEs may be multiplexed throughout an REG mapping that is appliedto different symbol periods. An REG according to the first configurationmay span 6 REs, where three of the REs may be used for reference signals(RS), and three of the REs may be used for UL control information orother data.

A second UL control configuration may use frequency divisionmultiplexing (FDM) for multiplexing different UEs. This configurationmay be associated with medium or large payloads and may provide forincreased spatial diversity over a single-carrier frequency-divisionmultiple access (SC-FDMA) scheme because, for instance, resource blocksthat are non-contiguous in the frequency domain may be used. In somecases, the operating environment may determine the UL controlconfiguration. For example, the second configuration may be used forchannels where frequency diversity and aligned REG sizes are conduciveto the configuration (e.g., the second configuration may be usedopportunistically). An REG according to the second configuration mayalso span 6 REs, but two of the REs may be used for RS and four of theREs may be used for UL control information or other data.

Aspects of the disclosure introduced above are described below in thecontext of a wireless communication system. Specific examples thenprovide additional detail regarding the first and second UL control andREG configurations. Aspects of the disclosure are further illustrated byand described with reference to apparatus diagrams, system diagrams, andflowcharts that relate to uplink control channel for low latencycommunications.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE)/LTE-Advanced (LTE-A) network.Wireless communications system 100 may support communication on an OFDMuplink control channel mapped to a set of REGs in which each REG ismapped to a portion of a different RB within a set of RBs.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude uplink transmissions from a UE 115 to a base station 105, ordownlink transmissions, from a base station 105 to a UE 115. UEs 115 maybe dispersed throughout the wireless communications system 100, and eachUE 115 may be stationary or mobile. A UE 115 may also be referred to asa mobile station, a subscriber station, a remote unit, a wirelessdevice, an access terminal (AT), a handset, a user agent, a client, orlike terminology. A UE 115 may also be a cellular phone, a wirelessmodem, a handheld device, a personal computer, a tablet, a personalelectronic device, a machine type communication (MTC) device, or thelike. Some UEs 115 may support low latency communications usingtransmission time intervals (TTIs) that have a shorter duration relativeto TTIs used by other UEs 115. UEs 115 that are configured for orcapable of low latency communications may be referred to as low latencyUEs 115, while other UEs 115 may be referred to as non-low latency UEs115 or legacy UEs 115.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as eNodeBs (eNBs) 105. Various base stations 105may be capable of low latency communications.

A frame structure may be used to organize physical resources (e.g.,radio resources in the frequency domain and the time domain). A framemay be a 10 ms interval that may be further divided into 10 equallysized sub-frames. Each sub-frame may include two consecutive time slots.Each slot may include 6 or 7 OFDMA symbol periods. A resource element(RE) consists of one symbol period and one subcarrier (a 15 KHzfrequency range). A resource block (RB) may contain 12 subcarriers thatare contiguous in the frequency domain and, for a normal cyclic prefixin each OFDM symbol period, 7 consecutive OFDM symbol periods in thetime domain (1 slot), or 84 resource elements. Some resource elementsmay include DL reference signals (DL-RS). The DL-RS may include acell-specific reference signal (CRS) and a UE-specific RS (UE-RS). UE-RSmay be transmitted on the resource blocks associated with a physicaldownlink shared channel (PDSCH). The number of bits carried by eachresource element may depend on the modulation scheme (e.g., theconfiguration of resource elements that may be selected during eachsymbol period). Thus, the more resource blocks that a UE receives andthe higher the modulation scheme, the higher the data rate may be.

Downlink control information may be transmitted from a base station 105to a UE 115 using a physical downlink control channel (PDCCH). PDCCH maycarry downlink control information (DCI) in control channel elements(CCEs), which may consist of nine logically contiguous resource elementgroups (REGs), where each REG contains 4 resource elements (REs), forexample. DCI may include information regarding DL schedulingassignments, UL resource grants, transmission scheme, UL power control,HARQ information, MCS, and other information. The size and format of theDCI messages can differ depending on the type and amount of informationthat is carried by the DCI. For example, if spatial multiplexing issupported, the size of the DCI message may be large compared tocontiguous frequency allocations. Similarly, for a system that employsMIMO, the DCI must include additional signaling information. DCI sizeand format may depend on the amount of information as well as factorssuch as bandwidth, the number of antenna ports, and duplexing mode.

Uplink control information may be transmitted from a UE 115 to a basestation 105 using a physical uplink control channel (PUCCH). PUCCH maybe used for UL acknowledgements (ACKs), scheduling requests (SRs),channel quality indicators (CQI), and other UL control information. Insome cases, a PUCCH may be mapped to a control channel defined by a codeand two consecutive resource blocks. UL control signaling may depend onthe presence of timing synchronization for a cell. PUCCH resources forSR and CQI reporting may be assigned (and revoked) through RRCsignaling. In some cases, resources for SR may be assigned afteracquiring synchronization through a random access channel (RACH)procedure. In other cases, an SR may not be assigned to a UE 115 throughthe RACH (i.e., synchronized UEs may or may not have a dedicated SRchannel). PUCCH resources for SR and CQI may be lost when the UE is nolonger synchronized.

In some cases, PUCCH is transmitted using single carrier frequencydivision multiple access (SC-FDMA), but in other cases OFDM or othermultiplexing configurations may be used (e.g., for low latencycommunications). For low latency communications, PUCCH may also beorganized according to REGs as described herein. Control channels forlow latency communications (e.g., low latency PUCCH) may or may not bemapped to consecutive or contiguous RBs.

In some cases, wireless communications system 100 may utilize anenhanced CC (eCC), or more than one eCC. An eCC may be characterized byone or more features including: wider bandwidth, shorter symbolduration, shorter transmission time interval (TTI), and modified controlchannel configuration. In some cases, an eCC may be associated with acarrier aggregation configuration or a dual connectivity configuration(e.g., when multiple serving cells have a suboptimal or non-idealbackhaul link). An eCC may also be configured for use in unlicensedspectrum or shared spectrum (where more than one operator is allowed touse the spectrum). An eCC characterized by wide bandwidth may includeone or more segments that may be utilized by UEs 115 that are notcapable of monitoring the whole bandwidth or prefer to use a limitedbandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than othercomponent carriers (CCs), which may include use of a reduced symbolduration as compared with symbol durations of the other CCs. A shortersymbol duration is associated with increased subcarrier spacing. Adevice, such as a UE 115 or base station 105, utilizing eCCs maytransmit wideband signals (e.g., 20, 40, 60, 80 MHz, etc.) at reducedsymbol durations (e.g., 16.67 μs). A TTI in eCC may consist of one ormultiple symbols. In some cases, the TTI duration (that is, the numberof symbols in a TTI) may be variable.

A UE 115 or a base station 105 may identify a set of REGs for lowlatency communication, where each REG may include a portion of adifferent RB of a set of RBs, wherein RBs of the set of RBs may becontiguous or non-contiguous. The device may then map an uplink controlchannel for to the selected REGs and communicate on the uplink controlchannel accordingly. Reference signals may also be transmitted in thesame RBs, and the REGs may be mapped around the resources used forreference signals. In some cases, multiple UEs 115 may transmit uplinkcontrol data using the same resources using code division multiplexing(CDM) (e.g., if the control payload is relatively small). In othercases, multiple UEs may be frequency division multiplexed (FDM).

FIG. 2 illustrates an example of a wireless communications system 200that supports an uplink control channel for low latency communications,in accordance with aspects of the present disclosure. Wirelesscommunications system 200 may include base station 105-a and UEs 115-aand 115-b, which may be examples of the corresponding devices describedwith reference to FIG. 1. Wireless communications system 200 may supportcommunication on UL control channels mapped to a set of REGs.

Wireless communications system 200 may use a reduced or variable TTIduration to reduce latency between DL and UL transmissions (i.e., lowlatency operation). In some cases, a low latency TTI may correspond toone LTE symbol period or approximately 71 μs for normal cyclic prefix(CP) and approximately 83 μs for extended CP. However, other TTIdurations are possible (e.g., two LTE symbol periods, 1 slot, etc.).

Some wireless communications systems may use SC-FDMA for communicationsby multiple wireless devices. Additionally or alternatively, wirelesscommunications system 200 may use OFDM or other multiplexing techniques.For example, multiple UEs 115, such as UE 115-a and UE 115-b, maytransmit uplink control data using OFDM based on orthogonal subcarrierfrequencies and symbol periods (e.g., the tone spacing may be inverselyproportional to the symbol length). This may increase communicationefficiency or reduce implementation costs in certain cases. For example,when a quantity of small cells found in a geographic region increases,the quantity of UEs 115 served by a given base station 105 maycorrespondingly decrease. Certain design characteristics and componentsof base stations 105 and UEs 115 may also be similar (e.g., due toservices designed for device-to-device communication, vehicle-to-vehiclecommunication, etc.). Using common communication capabilities for basestations 105 and UEs 115 may support reduced implementation andoperation costs.

Wireless communications system 200 may use OFDM-based low latencycommunication for UL transmission, which may coexist with other ULtransmissions (e.g., traffic that includes a PUCCH, a physical uplinkshared channel (PUSCH), a SRS, a physical random access channel (PRACH),etc.) in the same subframe or symbol period. While DL transmissions canutilize a cell specific reference signal (CRS) common to all UEs 115, aUL reference signal may be UE-specific. As a result, the UL RS may haveaspects similar to those of a DL demodulation reference signal (DM-RS).UL transmissions may also have aspects similar to those of a CRS, wheredifferent UEs 115 (e.g., UE 115-a and UE 115-b) may have differentfrequency offsets, symbol period offsets, cyclic shifts, etc. In somecases, reference signals (RS) and data may be overlaid in the samemodulation symbol.

In some cases, transmissions that contain PUCCH with CDM characteristicsmay be more efficient than transmission using FDM due to an amount ofcontrol data in DL transmissions. For example, in carrier aggregation(CA) and enhanced CA (eCA), which may use a large number of componentcarriers (CCs), the differences may become smaller based on the amountof control data used (e.g., in some cases CA transmissions may containmore UL control information). In some cases, SRS transmissions may alsobe used.

In one example, UL communication links (e.g., UL communication links210-a and 210-b) may include a control channel that uses SC-FDMA, anddata may be multiplexed using OFDM. This type of configuration mayaddress link budget limitations, and may result in less resourcefragmentation. Alternatively, a configuration based on OFDM may be used.In these cases, a RS design may have aspects similar to those of a CRS,where different UEs may be associated with different frequency offsets.

For example, the equation mod(C-RNTI,3) may be used to determine afrequency offset based on a cell specific radio network temporaryidentity (C-RNTI) (e.g., using tow antennas). In some examples, thefrequency offset can be configured or indicated based on the specific UE115. A dynamic indication (e.g., in a downlink control channel) maysupport multiplexing of different UEs 115 in the same RB. The presenceof RS design may also be determined based on a combination ofsemi-static and dynamic indications. For example, in symbols 0/4/7/11 ofa given subframe, an RS may always be transmitted if UE 115-a or UE115-b transmits PUCCH. If the first PUCCH transmission in a symbol isnot 0/4/7/11, an RS may be determined based on other considerations. Forinstance, RS presence may be based on a fixed location, and subsequentoccurrences of an RS may be mapped to resources based on a firstoccurrence of the RS.

Different UL channel configurations may be used when OFDM is employedfor an UL control channel. In what may be referred to as Type 1 controlchannel, the UL control information may be mapped to REGs that arefrequency distributed (i.e., having REs that are non-contiguous in thefrequency domain) and use CDM. In some examples, a Type 1 controlchannel may be associated with relatively small payloads, and differentUEs 115 may be multiplexed in the same RE.

In what may be referred to as a Type 2 control channel, the UL controlinformation may be mapped to REGs within a CCE and may use FDM formultiple UEs. In some examples, Type 2 control channels may beassociated with a medium or large payload, and different UEs 115 may notbe multiplexed in the same RE (e.g., using CDM). In some cases, theoperating environments for Type 1 control channels may be different thanfor Type 2 control channels.

With a Type 1 control channel used for UL communications, there may beCDM for RS REs, CDM for data REs (e.g., REs that include data or controlinformation rather than reference signal), and frequency diversity. Inone example, each REG may span six REs that consist of three RS REs andthree data REs in an interleaved manner. In some examples, symbols mayhave RS or data, where symbols including data may be relatively morefrequent in the event that a RS from an earlier symbol can be used forcontrol data demodulation.

In some examples, a length-3 discrete Fourier transform (DFT) may beused for CDM operation. For example, three different sequences may beidentified using the cover codes:

$\left\lbrack {1,1,1} \right\rbrack,\left\lbrack {1,{\exp \left( {j*2*{{pi}/3}} \right)},{\exp \left( {j*4*{{pi}/3}} \right)}} \right\rbrack,{{{and}\mspace{14mu}\left\lbrack {1,{\exp \left( {j*4*\frac{pi}{3}} \right)},{\exp \left( {j*2*\frac{pi}{3}} \right)}} \right\rbrack}.}$

Individual UEs may determine one of the three sequences to use (e.g.,based on the starting resource of a downlink control channel, a PDSCHblock index, information fields in the control channel, etc.).

Each control channel may include a number of REGs (e.g., three or four),where the associated mapping of REs across RBs can be configured,indicated by base station 105-a, or dynamically determined. The RBs maybe frequency distributed (e.g., non-contiguous in the frequency domain).For example, if a transmission includes a one-bit scheduling request(SR), there may be radio resource control (RRC) configured resources.Additionally or alternately, if a hybrid automatic repeat request (HARD)acknowledgment (ACK) is included, the resources may be dynamicallydetermined based on a PDCCH or PDSCH, or both).

In Type 1 control channel designs, either one symbol or more than onesymbol may be used for the control channel transmissions. When using aone-symbol control channel, the control channel may span four RBs in asymbol period, where each RB includes one REG that contains RS REs anddata REs that are interleaved in the frequency domain. A second symbolperiod that follows the symbol period of the control channel may alsospan four RBs, each with one REG of data only, where the RS located inthe first symbol period may be used for demodulation of the secondsymbol period. For the second symbol period, the length-3 DFT can beused (for three interleaved REs) or, alternatively, an orthogonalsequence of length 6 may be used. In examples where two symbol periodsare used, each symbol period may span two RBs in each symbol period,each symbol period with one REG. In some examples, there may be moretime-diversity using two symbol periods as compared to control channelsusing a single symbol period.

In some cases, UL REG configurations may be UE-specific and may bedifferent from a DL REG. For example, some REGs may have three RS REsand three data REs (e.g., REs carrying control information or data) foran REG in a symbol period. But another UE 115 may have an REG with sixcontrol REs or six data REs in the same symbol period (but in differentREs). That is, in some examples, a first UE 115-a may have an REG withsix control data REs in a RB in a symbol period, while a second UE 115-bmay have an REG with three RS REs and three control data REs in the sameRB of the same symbol period.

In another configuration (i.e., a Type 2), control channels used for ULcommunications may be based on FDM. Type 2 channels may be configuredfor frequency diversity and based on aligned REG sizes (e.g., REG sizesbeing aligned with other control channels). In some examples of Type 2channels, each REG may include six REs, including two RS REs and fourdata REs in an interleaved manner. The configuration of Type 2 controlchannels maybe different from Type 1 control channels discussed above,or may incorporate similar aspects of the Type 1 design.

In some examples, transmitted symbols may have either a RS or data, orboth, where data may be more numerous in cases where a RS from anearlier symbol period can be used for control data demodulation. Eachcontrol channel may have one or more CCE, each including three or fourREGs, where the RB locations may be configured or indicated, and may befrequency distributed. For example, if one CCE is used, three REGs mayallow for 12 control data REs per CCE, and up to 18 REGs may be used ifeach REG has six control data REs. Alternatively, if one CCE is used,three REGs may allow for 16 control data REs per CCE, and up to 24 REGsmay be possible if each REG has six control data REs.

As an example of the RS per REG configuration for Type 2 controlchannels, there may be RS REs and data REs interleaved in the frequencydomain as mentioned above; but in some cases there may be two RS REs andfour data REs within the REG, where one CCE may have three REGs whenusing one symbol control channels. In the first symbol period, three RBsmay be used, each with one REG containing interleaved RS and data. Thesecond symbol period may include three RBs, each with one REG containingdata, which can utilize RSs of the previous symbol period fordemodulation. In some cases, different RS patterns may be used (e.g.,instead of a sequence of one RS RE, followed by two data REs, followedby one RS RE, followed by two data REs (i.e., “RDDRDD”) in an REG, asequence of one RS RE, followed by four data REs, followed by one RS RE(i.e., “RDDDDR”) in an REG may be employed). When two or more symbolperiods are used for the control channel, for example, its REGs may beidentified from different symbol periods for increased time diversity.

In some cases, the CCE mapping for the control channel may besemi-statically configured, dynamically determined or indicated, or acombination of both. CCE location may further depend on the combinationsof uplink control information (UCI) transmitted on the control channel.In some cases, for channel state information (CSI) or scheduling request(SR) feedback, the CCE can be indicated via an RRC configuration. Forhybrid automatic HARQ feedback, dynamic indication/determination may beused, which may be linked with PDCCH or PDSCH, or both. In someexamples, the number of CCEs can be semi-statically configured ordynamically derived and there may be a dependence on combinations of UCIand the respective payload size.

In some cases, when UE 115 has two or more transmit antennas, an antennaselection, switching, or diversity-based operation may be used. Forexample, a UE 115 may pick the best antenna for an REG such as REG 2 forthe first antenna, and then REG 1 and REG 3 to the second antenna. TheUE 115 may also alternate the transmit port across REGs. Alternatively,the second transmit port may be associated with another set of REGs,which may be similar to spatial orthogonal resource transmit diversity(SORTD).

In some examples, a control channel may be transmitted using a waveformother than an OFDM waveform. That is, the Type 1 or Type 2 controlchannel designs may, for example, more efficiently use multi-clusterdiscrete Fourier transform spread OFDMA (DFT-S-OFDM) or interleavedfrequency division multiplexing (IFDM) for an improved peak to averagepower ratio (PAPR), and thus, better link efficiency. As a result, theremay be a multi-cluster/IFDM-based control channel as opposed to anOFDM-based control channel for a UE 115.

In some cases, the UL data channel design may determine RS placement.The placement may be similar to the RS design for OFDM-based controlchannel for some low latency PUSCH configurations. Low latency PUSCH maybe referred to as uPUSCH and low latency PUCCH may be referred to asuPUCCH. The RS for uPUCCH and uPUSCH may be shared, such as in rank 1uPUSCH transmissions. The RS density (e.g., spatial density, timedensity, or frequency density) can also be different from that of PUCCH,and CDM operation in time-domain may be necessary for higher rank uPUSCHtransmissions. In some cases, resource assignment can still be RB-based,where the DL resource allocation types may be readily re-used. However,the maximum bandwidth for uPUSCH can be different from the maximumpossible UL bandwidth where some RBs can be reserved for non-low latency(e.g., legacy) PUCCH operation.

In some cases, the last symbol in a subframe may be reserved for asounding reference signal (SRS) if the subframe is a cell-specific SRSsubframe. To coexist with some wireless systems, there may be supportfor two types of SRS. An RS for uPUCCH and uPUSCH may be used forsounding and support of SRS in the last symbol. Additionally oralternatively, compatibility between low latency operations (e.g.,uPUCCH configurations) and other system configuration may be maintainedby leveraging configurations used for non-low latency communications.For instance, an existing (e.g., non-low latency) physical random accesschannel may be re-used.

FIGS. 3A, 3B, and 3C illustrate examples of uplink control channelconfigurations 301, 302, and 303 for low latency communications. In somecases, uplink control channel configurations 301, 302, and 303 mayrepresent aspects of techniques performed by a UE 115 or base station105 as described with reference to FIGS. 1-2. FIGS. 3A-3C depict RBconfigurations for mapping uplink control channels to a set of REGs. TheRB locations may be configured differently for different transmissiontechniques, such as with Type 1 or Type 2 control channels, as discussedabove.

FIG. 3A illustrates an uplink control channel configuration 301 for aType 1 control channel transmission. For example, an UL transmissionduring first symbol period 305-a may span four RBs 310 that arenon-contiguous in the frequency domain, such as RB 310-a, where each RBmay include one REG. That is, RB 310-a may include REG 315-a, includingmultiple REs within RB 310-a that are interleaved (e.g., in alternatingsubcarriers, etc.) with RS REs 320-a. In some cases, REG 315-a maycontain six REs, including three RS REs 320-a and three data REs 325-a,where RS REs 320-a and data REs 325-a may be transmitted in aninterleaved manner. A length-3 discrete Fourier transform (DFT) (oranother DFT) may be used for CDM for multiplexing multiple UEs 115,where each UE 115 may determine a sequence to use based on DL PDSCHblock index, information fields in PDCCH, and the like.

In some cases, REGs 315 of a second symbol period 305-b may include onlyRS REs or only data REs. For example, in second symbol period 305-b thatincludes four RBs 310-b, each RB 310-b may include an REG 315-bcontaining six data REs 325-b. In such cases, the RS(s) from an earliersymbol period (e.g., first symbol period 305-a) may be used for controldata demodulation. In some examples, REG 315-b may include six RS REs. Alength-3 DFT may be used for three interleaved REs, or alternatively, anew orthogonal sequence may be used. In some cases, a second portion 330of RB 310-a may be used for transmissions from one or more different UEs115.

FIG. 3B illustrates an uplink control channel configuration 302 for atwo-symbol Type 1 control channel transmission, where each symbol periodmay include REs from two RBs 310. For example, RB 310-c within a firstsymbol period 305-c may include REG 315-c that contains three RS REs320-b and three data REs 325-c that are interleaved in the frequencydomain. A second symbol period 305-d may contain RB 310-d that includessix data REs 325-d, and as discussed above, a reference signal from anearlier symbol period (e.g., first symbol period 305-c) may be used forcontrol demodulation. An REG may also include six RS REs, or acombination of RS REs and data REs. Two-symbol Type 1 control channeltransmissions may be associated with relatively greater time diversityas compared to one-symbol Type 1 control channel transmissions.

FIG. 3C illustrates an uplink control channel configuration 303 for aone-symbol Type 2 control channel transmission. For example, firstsymbol period 305-e may contain three RBs 310-e that include an REG315-e. REG 315-e may include RS REs 320-c and data REs 325-e that areinterleaved in the frequency domain, where there are two RS REs 320-cper REG 315-e. In some examples, different RS RE and data RE patternsmay be used in an REG 315-e. That is, an REG may contain REs followingthe pattern RDDDDR (where R indicates an RS RE and D indicates a dataRE). REs may also be organized according to the pattern RDDRDD, or someother pattern.

A second symbol period 305-f may similarly include three RBs 310-f thatinclude an REG 315-f. REG 315-f may contain data REs 325-f, or RS REs,or a combination of RS REs and data REs. In cases where only data REs325-f are included then a reference signal from a previous symbol period(e.g., first symbol period 305-e) may be used for demodulation of theREs of the second symbol period 305-f. In some cases, when two or moresymbol periods are used for the control channel communication, usingREGs from different symbol periods may correspond to increased timediversity.

FIG. 4 illustrates an example of a process flow 400 for systems thatsupport uplink control channel for low latency communications inaccordance with various aspects of the present disclosure. Process flow400 may include base station 105-b and UE 115-c, which may be examplesof the corresponding devices described with reference to FIG. 1-2.

At 405, UE 115-c and base station 105-b may establish a wirelesscommunication link (e.g., based on low latency operation, using a legacyPRACH procedure, or the like). The communication link may include bothuplink and downlink communications. The uplink communications mayinclude both user data and control data, which may also be referred toas control information.

At 410, UE 115-c and base station 105-b may identify a set of REGs forUL control transmissions, where each REG may include a portion of adifferent RB of a set of RBs (e.g., contiguous or non-contiguous RBs).In some cases, the set of REGs may be semi-statically configured usingRRC signaling. In some cases, the set of REGs may be dynamicallyconfigured using an indication communicated in a downlink message. EachREG may include a set of REs that include data REs and RS REs that areinterleaved in the frequency domain, where the interleaving may includealternating one or two of the control data REs with one of the RS REs.In some examples, UE 115-c and base station 105-b may identify an offset(e.g., a frequency offset, a symbol period offset, a cyclic shift,etc.), which may be applied to RS transmissions. The identified offsetmay be specifically associated with UE 115-c.

At 415, UE 115-c and base station 105-b may each map an uplink controlchannel for the wireless communication link to the set of REGs. In somecases UE 115-c and base station 105-b may determine a payload size ofthe uplink control channel and further identify a CDM cover code basedon the payload size. In some examples, UE 115-c and base station 105-bmay identify a quantity of REGs in the set of REGs based on a content ofthe uplink control channel.

At 420, UE 115-c may communicate with base station 105-b on the uplinkcontrol channel using the set of REGs. For example, UE 115-c maytransmit the uplink control information to base station 105-b. In somecases, UE 115-c may also transmit an uplink RS using an identifiedoffset in each RB of the set of RBs, where the uplink RS may betransmitted during symbol periods that include the uplink controlchannel at times indicated by base station 105-b. The uplink RS may beassociated with the uplink control channel or an uplink shared channel,or both.

In some cases, communicating over the wireless communication link may bebased on a CDM cover code. That is, multiple UEs 115 may be multiplexedin the UL control channel. In some examples, a waveform of the uplinkcontrol channel may include an OFDM waveform, a (discrete Fouriertransform spread) DFT-S-OFDM waveform, or an interleaved frequencydivision multiplexing (IFDM) waveform.

In some examples, communicating on the uplink control channel includestransmitting an RS and data in a first REG of the set of REGs during afirst symbol period and transmitting additional data in each RE of asecond REG of the set of REGs during a second symbol period that followsthe first symbol period. UE 115-c may identify a transmit antenna or atransmit port for each REG of the set of REGs and may also transmit aSRS during a last symbol period of a TTI that includes the uplinkcontrol channel.

FIG. 5 shows a block diagram of a wireless device 500 that supportsuplink control channel for low latency communications in accordance withvarious aspects of the present disclosure. Wireless device 500 may be anexample of aspects of a UE 115 or base station 105 described withreference to FIGS. 1, 2, and 4. Wireless device 500 may include receiver505, UL control manager 510, and transmitter 515. Wireless device 500may also include a processor. Each of these components may be incommunication with one another.

The receiver 505 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to uplinkcontrol channel for low latency communications, etc.). Information maybe passed on to other components of the device. The receiver 505 may bean example of aspects of the transceiver 825 described with reference toFIG. 8 or the transceiver 925 described with reference to FIG. 9.

The UL control manager 510 may identify a set of REGs, where each REG ofthe set of REGs may include a portion of a respective RB of a set ofRBs, map an uplink control channel for a wireless communication link tothe set of REGs, and communicate (e.g., in cooperation with the receiver505 and/or the transmitter 515) on the uplink control channel using theset of REGs. The UL control manager 510 may also be an example ofaspects of the UL control manager 805 described with reference to FIG. 8or the UL control manager 905 of FIG. 9. In some examples, the ULcontrol manager 510 is an aspect of the processor 810 described withreference to FIG. 8 or the processor 910 described with reference toFIG. 9.

The transmitter 515 may transmit signals received from other componentsof wireless device 500. In some examples, the transmitter 515 may becollocated with a receiver in a transceiver module. For example, thetransmitter 515 may be an example of aspects of the transceiver 825described with reference to FIG. 8 or the transceiver 925 described withreference to FIG. 9. The transmitter 515 may include a single antenna,or it may include a plurality of antennas.

FIG. 6 shows a block diagram of a wireless device 600 that supportsuplink control channel for low latency communications in accordance withvarious aspects of the present disclosure. Wireless device 600 may be anexample of aspects of a wireless device 500 or a UE 115 or base station105 described with reference to FIGS. 1, 2, 4, and 5. Wireless device600 may include receiver 605, UL control manager 610, and transmitter625. Wireless device 600 may also include a processor. Each of thesecomponents may be in communication with one another.

The receiver 605 may receive information which may be passed on to othercomponents of the device. The receiver 605 may also perform thefunctions described with reference to the receiver 505 of FIG. 5. Thereceiver 605 may be an example of aspects of the transceiver 825described with reference to FIG. 8 or the transceiver 925 described withreference to FIG. 9.

The UL control manager 610 may be an example of aspects of UL controlmanager 510 described with reference to FIG. 5. The UL control manager610 may include REG identifying component 615 and UL control channelcomponent 620. The UL control manager 610 may be an example of aspectsof the UL control manager 805 described with reference to FIG. 8 or theUL control manager 905 of FIG. 9. In some examples, the UL controlmanager 510 is an aspect of the processor 810 described with referenceto FIG. 8 or the processor 910 described with reference to FIG. 9.

The REG identifying component 615 may identify a quantity of REGs in theset of REGs based at least in part on a content of the uplink controlchannel, and identify a set of REGs, where each REG of the set of REGsmay include a portion of a respective RB of a set of RBs. In some cases,the set of REGs is semi-statically configured according to an indicationcommunicated using RRC signaling. In some cases, the set of REGs isdynamically configured using an indication communicated in a downlinkmessage. Each REG of the set of REGs may include a set of REs thatinclude data interleaved with REs that include a reference signal, wherethe interleaving may, in turn, include alternating one of the REs thatinclude data with one of the REs that include the reference signalduring a symbol period of an RB of the set of RBs.

In some cases, each REG of the set of REGs includes a set of REs thatinclude data interleaved with REs that include a reference signal, wherethe interleaving includes alternating two of the REs that include datawith one of the REs that include the reference signal during a symbolperiod of an RB of the set of RBs. In some cases, the set of RBs isnon-contiguous.

The UL control channel component 620 may map an uplink control channelfor a wireless communication link to the set of REGs and communicate(e.g., in cooperation with the receiver 605 and/or transmitter 625) onthe uplink control channel using the set of REGs. In some cases, thecommunicating includes transmitting a reference signal and first data ina first REG of the set of REGs during a first symbol period andtransmitting second data in each RE of a second REG of the set of REGsduring a second symbol period that follows the first symbol period. Insome cases, a waveform of the uplink control channel includes an OFDMwaveform, a DFT-S-OFDM waveform, or an IFDM waveform.

The transmitter 625 may transmit signals received from other componentsof wireless device 600. In some examples, the transmitter 625 may becollocated with a receiver in a transceiver module. For example, thetransmitter 625 may be an example of aspects of the transceiver 825described with reference to FIG. 8 or the transceiver 925 described withreference to FIG. 9. The transmitter 625 may utilize a single antenna,or it may utilize a plurality of antennas.

FIG. 7 shows a block diagram of a UL control manager 700, which may bean example of the corresponding component of wireless device 500 orwireless device 600. That is, UL control manager 700 may be an exampleof aspects of UL control manager 510 or UL control manager 610 describedwith reference to FIGS. 5 and 6. The UL control manager 700 may also bean example of aspects of the UL control manager 805 described withreference to FIG. 8 or the UL control manager 905 of FIG. 9. In someexamples, the UL control manager 510 is an aspect of the processor 810described with reference to FIG. 8 or the processor 910 described withreference to FIG. 9.

The UL control manager 700 may include REG identifying component 705, ULcontrol channel component 710, UL RS component 715, CDM component 720,antenna identifying component 725, SRS component 730, and REG structurecomponent 735. Each of these modules may communicate, directly orindirectly, with one another (e.g., via one or more buses).

The REG identifying component 705 may identify a quantity of REGs in aset of REGs based on a content of the uplink control channel, andidentify a set of REGs, where each REG of the set of REGs includes aportion of a respective RB of a set of RBs.

The UL control channel component 710 may map an uplink control channelfor a wireless communication link to the set of REGs, and communicate(e.g., in cooperation with a receiver 505 or 605 and/or transmitter 515or 625) on the uplink control channel using the set of REGs. In someexamples the UL control channel component may transmit data in each REof an REG of the set of REGs,

The UL RS component 715 may identify an offset associated with a UE,and, in combination with transmitter 515 or 625, for instance, transmitan uplink reference signal using the offset in each RB of the set ofRBs. In some cases, the uplink reference signal is transmitted duringsymbol periods that include the uplink control channel. In some cases,the uplink reference signal is transmitted during symbol periodsindicated by a base station. The uplink reference signal may beassociated with the uplink control channel or an uplink shared channel,or both.

The CDM component 720 may identify a code division multiplexing (CDM)cover code, where communicating over the wireless communication link isbased on the CDM cover code, and determine a payload size of the uplinkcontrol channel, where identifying the CDM cover code may be based onthe payload size. In some examples the CDM cover code may includeresource elements of two or more different subcarriers in the frequencydomain, or resource elements of two or more different symbol periods inthe time domain, or a combination thereof.

The antenna identifying component 725 may identify a transmit antenna ora transmit port (e.g., of a transmitter 515 or 625) for each REG of theset of REGs. The SRS component 730 may, in combination with transmitter515 or 625, for instance, transmit a SRS during a last symbol period ofa transmission time interval that includes the uplink control channel.

The REG structure component 735 may identify a first REG structureassociated with a first UE and a second REG structure associated with asecond UE, receive, in combination with receiver 505 or 605, forinstance, a first uplink reference signal from the first UE using thefirst REG structure in an RB of the set of RBs, receive, in combinationwith receiver 505 or 605, a second uplink reference signal from thesecond UE using the second REG structure in an RB of a set of RBs, andreceive, in combination with receiver 505 or 605, data or controlinformation in each RE of an REG associated with the first UE in anotherRB during a second symbol duration. In some cases, the first REGstructure and the second REG structure differ at least in one of afrequency offset, a number of REs for reference signals, or a CDM cover.

FIG. 8 shows a diagram of a system 800 including a device that supportsuplink control channel for low latency communications in accordance withvarious aspects of the present disclosure. For example, system 800 mayinclude UE 115-d, which may be an example of a wireless device 500, awireless device 600, or a UE 115 as described with reference to FIGS. 1,2, 4, and 5 through 7. UE 115-d may also include UL control manager 805,processor 810, memory 815, transceiver 825, antenna 830, and ECC module835. Each of these modules may communicate, directly or indirectly, withone another (e.g., via one or more buses). The UL control manager 805may be an example of an UL control manager 510, 610, or 700 as describedwith reference to FIGS. 5 through 7.

The processor 810 may include an intelligent hardware device, (e.g., acentral processing unit (CPU), a microcontroller, an applicationspecific integrated circuit (ASIC), etc.) The memory 815 may includerandom access memory (RAM) and read only memory (ROM). The memory 815may store computer-readable, computer-executable software includinginstructions that, when executed, cause the processor, and thus UE115-d, to perform various functions described herein (e.g., uplinkcontrol channel for low latency communications, etc.). In some cases,the software 820 may not be directly executable by the processor but maycause a computer (e.g., when compiled and executed) to perform functionsdescribed herein.

The transceiver 825 may communicate bi-directionally, via one or moreantennas, wired, or wireless links, with one or more networks, asdescribed above. For example, the transceiver 825 may communicatebi-directionally with a base station 105 (e.g., base station 105-c) or aUE 115. The transceiver 825 may also include a modem to modulate thepackets and provide the modulated packets to the antennas fortransmission, and to demodulate packets received from the antennas. Insome cases, the wireless device may include a single antenna 830.However, in some cases the device may have more than one antenna 830,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The ECC module 835 may enable operations using ECCs such ascommunication using shared or unlicensed spectrum, using reduced TTIs orsubframe durations, or using a large number of component carriers.

FIG. 9 shows a diagram of a wireless system 900 including a device thatsupports uplink control channel for low latency communications inaccordance with various aspects of the present disclosure. For example,wireless system 900 may include base station 105-d, which may be anexample of a wireless device 500, a wireless device 600, or a basestation 105 as described with reference to FIGS. 1, 2, 4, and 5 through7. Base station 105-d may also include components for bi-directionalvoice and data communications including components for transmittingcommunications and components for receiving communications. For example,base station 105-d may communicate bi-directionally with one or more UEs115.

Base station 105-d may also include UL control manager 905, processor910, memory 915, transceiver 925, antenna 930, base stationcommunications module 935, and network communications module 940. Eachof these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses). The UL control manager 905 may bean example of a UL control manager as described with reference to FIGS.5 through 7.

The processor 910 may include an intelligent hardware device, (e.g., aCPU, a microcontroller, an ASIC, etc.) The memory 915 may include RAMand ROM. The memory 915 may store computer-readable, computer-executablesoftware including instructions that, when executed, cause theprocessor, and thus base station 105-d, to perform various functionsdescribed herein (e.g., uplink control channel for low latencycommunications, etc.). In some cases, the software 920 may not bedirectly executable by the processor but may cause a computer (e.g.,when compiled and executed) to perform functions described herein.

The transceiver 925 may communicate bi-directionally, via one or moreantennas, wired, or wireless links, with one or more networks, asdescribed above. For example, the transceiver 925 may communicatebi-directionally with a base station 105 (e.g., base stations 105-e or105-f) or a UE 115 (e.g., UEs 115-e or 115-f). The transceiver 925 mayalso include a modem to modulate the packets and provide the modulatedpackets to the antennas for transmission, and to demodulate packetsreceived from the antennas. In some cases, the wireless device mayinclude a single antenna 930. However, in some cases the device may havemore than one antenna 830, which may be capable of concurrentlytransmitting or receiving multiple wireless transmissions.

The base station communications module 935 may manage communicationswith other base station 105 (e.g., base stations 105-e or 105-f), andmay include a controller or scheduler for controlling communicationswith UEs 115 (e.g., UEs 115-e or 115-f) in cooperation with other basestations 105. For example, the base station communications module 935may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, base station communications module 935may provide an X2 interface within an LTE/LTE-A wireless communicationnetwork technology to provide communication between base stations 105.

The network communications module 940 may manage communications with thecore network (e.g., via one or more wired backhaul links). For example,the network communications module 940 may manage the transfer of datacommunications for client devices, such as one or more UEs 115.

FIG. 10 shows a flowchart illustrating a method 1000 for uplink controlchannel for low latency communications in accordance with variousaspects of the present disclosure. The operations of method 1000 may beimplemented by a UE 115 or base station 105 or its components asdescribed with reference to FIG. 1, 2, 4, 8, or 9. For example, theoperations of method 1000 may be performed by the UL control manager asdescribed herein. In some examples, the UE 115 or base station 105 mayexecute a set of codes to control the functional elements of the deviceto perform the functions described below. Additionally or alternatively,the UE 115 or base station 105 may perform aspects the functionsdescribed below using special-purpose hardware.

At block 1005, the UE 115 or base station 105 may identify a set ofREGs, where each REG of the set of REGs includes a portion of arespective RB of a set of RBs as described above with reference to FIGS.2 through 4. In certain examples, the operations of block 1005 may beperformed by the REG identifying component 615 or 705 as described withreference to FIGS. 6 and 7. In some examples, the operations of block1005 may be performed by the processor 810 or 910 as described withreference to FIGS. 8 and 9.

At block 1010, the UE 115 or base station 105 may map an uplink controlchannel for a wireless communication link to the set of REGs asdescribed above with reference to FIGS. 2 through 4. In certainexamples, the operations of block 1010 may be performed by the ULcontrol channel component as described with reference to FIGS. 6 and 7.In some examples, the operations of block 1010 may be performed by theprocessor 810 or 910 as described with reference to FIGS. 8 and 9.

At block 1015, the UE 115 or base station 105 may communicate on theuplink control channel using the set of REGs as described above withreference to FIGS. 2 through 4. In certain examples, the operations ofblock 1015 may be performed by the UL control channel component asdescribed with reference to FIGS. 6 and 7. In some examples, theoperations of block 1015 may be performed by the transceiver 825 or 925as described with reference to FIGS. 8 and 9.

FIG. 11 shows a flowchart illustrating a method 1100 for uplink controlchannel for low latency communications in accordance with variousaspects of the present disclosure. The operations of method 1100 may beimplemented by a UE 115 or base station 105 or its components asdescribed with reference to FIG. 1, 2, 4, 8, or 9. For example, theoperations of method 1100 may be performed by the UL control manager asdescribed herein. In some examples, the UE 115 or base station 105 mayexecute a set of codes to control the functional elements of the deviceto perform the functions described below. Additionally or alternatively,the UE 115 or base station 105 may perform aspects the functionsdescribed below using special-purpose hardware.

At block 1105, the UE 115 or base station 105 may identify a set ofREGs, where each REG of the set of REGs includes a portion of arespective RB of a set of RBs as described above with reference to FIGS.2 through 4. In certain examples, the operations of block 1105 may beperformed by the REG identifying component as described with referenceto FIGS. 6 and 7. In some examples, the operations of block 1105 may beperformed by the processor 810 or 910 as described with reference toFIGS. 8 and 9.

At block 1110, the UE 115 or base station 105 may identify an offsetassociated with a UE as described above with reference to FIGS. 2through 4. In certain examples, the operations of block 1110 may beperformed by the UL RS component as described with reference to FIGS. 6and 7. In some examples, the operations of block 1110 may be performedby the processor 810 or 910 as described with reference to FIGS. 8 and9.

At block 1115, the UE 115 or base station 105 may map an uplink controlchannel for a wireless communication link to the set of REGs asdescribed above with reference to FIGS. 2 through 4. In certainexamples, the operations of block 1115 may be performed by the ULcontrol channel component as described with reference to FIGS. 6 and 7.In some examples, the operations of block 1115 may be performed by theprocessor 810 or 910 as described with reference to FIGS. 8 and 9.

At block 1120, the UE 115 or base station 105 may communicate on theuplink control channel using the set of REGs, where an uplink referencesignal is transmitted using the offset in each RB of the set ofnon-contiguous RBs is transmitted over symbol periods of the uplinkcontrol channel, as described above with reference to FIGS. 2 through 4.In certain examples, the operations of block 1120 may be performed bythe UL control channel component as described with reference to FIGS. 6and 7. In some examples, the operations of block 1120 may be performedby the transceiver 825 or 925 as described with reference to FIGS. 8 and9

FIG. 12 shows a flowchart illustrating a method 1200 for uplink controlchannel for low latency communications in accordance with variousaspects of the present disclosure. The operations of method 1200 may beimplemented by a UE 115 or base station 105 or its components asdescribed with reference to FIG. 1, 2, 4, 8, or 9. For example, theoperations of method 1200 may be performed by the UL control manager asdescribed herein. In some examples, the UE 115 or base station 105 mayexecute a set of codes to control the functional elements of the deviceto perform the functions described below. Additionally or alternatively,the UE 115 or base station 105 may perform aspects the functionsdescribed below using special-purpose hardware.

At block 1205, the UE 115 or base station 105 may identify a set ofREGs, where each REG of the set of REGs includes a portion of arespective RB of a set of RBs as described above with reference to FIGS.2 through 4. In certain examples, the operations of block 1205 may beperformed by the REG identifying component as described with referenceto FIGS. 6 and 7. In some examples, the operations of block 1205 may beperformed by the processor 810 or 910 as described with reference toFIGS. 8 and 9.

At block 1210, the UE 115 or base station 105 may map an uplink controlchannel for a wireless communication link to the set of REGs asdescribed above with reference to FIGS. 2 through 4. In certainexamples, the operations of block 1210 may be performed by the ULcontrol channel component as described with reference to FIGS. 6 and 7.In some examples, the operations of block 1210 may be performed by theprocessor 810 or 910 as described with reference to FIGS. 8 and 9.

At block 1215, the UE 115 or base station 105 may determine a payloadsize of the uplink control channel as described above with reference toFIGS. 2 through 4. In certain examples, the operations of block 1215 maybe performed by the CDM component as described with reference to FIGS. 6and 7. In some examples, the operations of block 1215 may be performedby the processor 810 or 910 as described with reference to FIGS. 8 and9.

At block 1220, the UE 115 or base station 105 may identify a codedivision multiplexing (CDM) cover code, where identifying the CDM covercode is based on the payload size as described above with reference toFIGS. 2 through 4. In certain examples, the operations of block 1220 maybe performed by the CDM component as described with reference to FIGS. 6and 7. In some examples, the operations of block 1220 may be performedby the processor 810 or 910 as described with reference to FIGS. 8 and9.

At block 1225, the UE 115 or base station 105 may communicate on theuplink control channel using the set of REGs, where communicating overthe wireless communication link is based on the CDM cover code asdescribed above with reference to FIGS. 2 through 4. In certainexamples, the operations of block 1225 may be performed by the ULcontrol channel component as described with reference to FIGS. 6 and 7.In some examples, the operations of block 1225 may be performed by thetransceiver 825 or 925 as described with reference to FIGS. 8 and 9.

FIG. 13 shows a flowchart illustrating a method 1300 for uplink controlchannel for low latency communications in accordance with variousaspects of the present disclosure. The operations of method 1300 may beimplemented by a UE 115 or base station 105 or its components asdescribed with reference to FIG. 1, 2, 4, 8, or 9. For example, theoperations of method 1300 may be performed by the UL control manager asdescribed herein. In some examples, the UE 115 or base station 105 mayexecute a set of codes to control the functional elements of the deviceto perform the functions described below. Additionally or alternatively,the UE 115 or base station 105 may perform aspects the functionsdescribed below using special-purpose hardware.

At block 1305, the UE 115 or base station 105 may identify a set ofREGs, where each REG of the set of REGs includes a portion of arespective RB of a set of RBs as described above with reference to FIGS.2 through 4. In certain examples, the operations of block 1305 may beperformed by the REG identifying component as described with referenceto FIGS. 6 and 7. In some examples, the operations of block 1305 may beperformed by the processor 810 or 910 as described with reference toFIGS. 8 and 9.

At block 1310, the UE 115 or base station 105 may map an uplink controlchannel for a wireless communication link to the set of REGs asdescribed above with reference to FIGS. 2 through 4. In certainexamples, the operations of block 1310 may be performed by the ULcontrol channel component as described with reference to FIGS. 6 and 7.In some examples, the operations of block 1310 may be performed by theprocessor 810 or 910 as described with reference to FIGS. 8 and 9.

At block 1315, the UE 115 or base station 105 may communicate on theuplink control channel using the set of REGs, where communicating overthe wireless communication link includes transmitting a reference signaland first data in a first REG of the set of REGs during a first symbolperiod, and transmitting second data in each RE of a second REG of theset of REGs during a second symbol period that follows the first symbolperiod as described above with reference to FIGS. 2 through 4. Incertain examples, the operations of block 1315 may be performed by theUL control channel component as described with reference to FIGS. 6 and7. In some examples, the operations of block 1315 may be performed bythe transceiver 825 or 925 as described with reference to FIGS. 8 and 9.

It should be noted that these methods describe possible implementation,and that the operations and the steps may be rearranged or otherwisemodified such that other implementations are possible. In some examples,aspects from two or more of the methods may be combined. For example,aspects of each of the methods may include steps or aspects of the othermethods, or other steps or techniques described herein. Thus, aspects ofthe disclosure may provide for uplink control channel for low latencycommunications.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notto be limited to the examples and designs described herein but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more”) indicates an inclusive listsuch that, for example, a list of at least one of A, B, or C means A orB or C or AB or AC or BC or ABC (i.e., A and B and C).

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. The words “module,” “mechanism,”“element,” “device,” “component,” and the like may not be a substitutefor the word “means.” As such, no claim element is to be construed as ameans plus function unless the element is expressly recited using thephrase “means for.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media caninclude RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk, and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA) (FDMA), orthogonal frequency division multiple access (OFDMA)(OFDMA), single carrier frequency division multiple access (SC-FDMA),and other systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as (Global System forMobile communications (GSM)). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),Institute of Electrical and Electronics Engineers (IEEE) 802.11(wireless fidelity (Wi-Fi)), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications system (Universal Mobile Telecommunications System(UMTS)). 3GPP LTE and LTE-advanced (LTE-A) are new releases of UMTS thatuse E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-a, and GSM are described indocuments from an organization named “Third Generation PartnershipProject” (3GPP). CDMA2000 and UMB are described in documents from anorganization named “Third Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the systems and radiotechnologies mentioned above as well as other systems and radiotechnologies. The description herein, however, describes an LTE systemfor purposes of example, and LTE terminology is used in much of thedescription above, although the techniques are applicable beyond LTEapplications.

In LTE/LTE-A networks, including networks described herein, the termevolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A network in which different typesof eNBs provide coverage for various geographical regions. For example,each eNB or base station may provide communication coverage for a macrocell, a small cell, or other types of cell. The term “cell” is a 3GPPterm that can be used to describe a base station, a carrier or componentcarrier (CC) associated with a base station, or a coverage area (e.g.,sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an access point(AP), a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a HomeeNodeB, or some other suitable terminology. The geographic coverage areafor a base station may be divided into sectors making up only a portionof the coverage area. The wireless communications system or systemsdescribed herein may include base station of different types (e.g.,macro or small cell base stations). The UEs described herein may be ableto communicate with various types of base stations and network equipmentincluding macro eNBs, small cell eNBs, relay base stations, and thelike. There may be overlapping geographic coverage areas for differenttechnologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base stations, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers (CCs)). A UE may be able to communicate withvarious types of base stations and network equipment including macroeNBs, small cell eNBs, relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The DL transmissions described herein may also be called forward linktransmissions while the UL transmissions may also be called reverse linktransmissions. Each communication link described herein including, forexample, wireless communications system 100 and 200 of FIGS. 1 and 2 mayinclude one or more carriers, where each carrier may be a signal made upof multiple sub-carriers (e.g., waveform signals of differentfrequencies). Each modulated signal may be sent on a differentsub-carrier and may carry control information (e.g., reference signals,control channels, etc.), overhead information, user data, etc. Thecommunication links described herein (e.g., communication links 125 ofFIG. 1) may transmit bidirectional communications using frequencydivision duplex (FDD) (e.g., using paired spectrum resources) or timedivision duplex (TDD) operation (e.g., using unpaired spectrumresources). Frame structures may be defined for FDD (e.g., framestructure type 1) and TDD (e.g., frame structure type 2).

Thus, aspects of the disclosure may provide for uplink control channelfor low latency communications. It should be noted that these methodsdescribe possible implementations, and that the operations and the stepsmay be rearranged or otherwise modified such that other implementationsare possible. In some examples, aspects from two or more of the methodsmay be combined.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, a field-programmable gatearray (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a digital signal processor (DSP) and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration). Thus, the functions describedherein may be performed by one or more other processing units (orcores), on at least one integrated circuit (IC). In various examples,different types of integrated circuits may be used (e.g.,Structured/Platform ASICs, an FPGA, or another semi-custom IC), whichmay be programmed in any manner known in the art. The functions of eachunit may also be implemented, in whole or in part, with instructionsembodied in a memory, formatted to be executed by one or more general orapplication-specific processors.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

As used herein, the phrase “based on” shall not be construed as areference to a closed set of conditions. For example, an exemplary stepthat is described as “based on condition A” may be based on both acondition A and a condition B without departing from the scope of thepresent disclosure. In other words, as used herein, the phrase “basedon” shall be construed in the same manner as the phrase “based at leastin part on.”

What is claimed is:
 1. A method of wireless communication comprising:identifying a set of resource element groups (REGs), wherein each REG ofthe set of REGs comprises a portion of a respective resource block (RB)of a set of RBs; mapping an uplink control channel for a wirelesscommunication link to the set of REGs; and communicating on the uplinkcontrol channel using the set of REGs.
 2. The method of claim 1, whereinthe set of RBs is non-contiguous.
 3. The method of claim 1, furthercomprising: identifying an offset associated with a user equipment (UE);and transmitting an uplink reference signal using the offset in each RBof the set of RBs.
 4. The method of claim 3, wherein the uplinkreference signal is transmitted during one or more symbol periods thatcomprise the uplink control channel.
 5. The method of claim 3, whereinthe uplink reference signal is transmitted during one or more symbolperiods indicated by a base station.
 6. The method of claim 3, whereinthe uplink reference signal is associated with the uplink controlchannel or an uplink shared channel, or both.
 7. The method of claim 1,wherein the set of REGs is semi-statically configured according to anindication communicated using RRC signaling.
 8. The method of claim 1,wherein the set of REGs is dynamically configured using an indicationcommunicated in a downlink message.
 9. The method of claim 1, wherein awaveform of the uplink control channel comprises an orthogonal frequencydivision multiplexing (OFDM) waveform, a discrete Fourier transformspread OFDM (DFT-S-OFDM) waveform, or an interleaved frequency divisionmultiplexing (IFDM) waveform.
 10. The method of claim 1, furthercomprising: identifying a code division multiplexing (CDM) cover code,wherein communicating over the wireless communication link is based atleast in part on the CDM cover code.
 11. The method of claim 10, whereinthe CDM cover code comprises resource elements of two or more differentsubcarriers in a frequency domain, or resource elements of two or moredifferent symbol periods in a time domain, or a combination thereof. 12.The method of claim 10, further comprising: determining a payload sizeof the uplink control channel, wherein identifying the CDM cover code isbased at least in part on the payload size.
 13. The method of claim 1,wherein each REG of the set of REGs comprises a set of resource elements(REs) that comprise data interleaved with REs that comprise a referencesignal, wherein the interleaving comprises alternating one of the REsthat comprise data with one of the REs that comprise the referencesignal during a symbol period of an RB of the set of RBs.
 14. The methodof claim 1, wherein each REG of the set of REGs comprises a set of REsthat comprise data interleaved with REs that comprise a referencesignal, wherein the interleaving comprises alternating two of the REsthat comprise data with one of the REs that comprise the referencesignal during a symbol period of an RB of the set of RBs.
 15. The methodof claim 1, further comprising: identifying a quantity of REGs in theset of REGs based at least in part on a content of the uplink controlchannel.
 16. The method of claim 1, wherein the communicating comprises:transmitting a reference signal and first data in a first REG of the setof REGs during a first symbol period; and transmitting second data ineach RE of a second REG of the set of REGs during a second symbol periodthat follows the first symbol period.
 17. The method of claim 1, furthercomprising: identifying a transmit antenna or a transmit port for eachREG of the set of REGs.
 18. The method of claim 1, wherein thecommunicating comprises: transmitting a sounding reference signal (SRS)during a last symbol period of a transmission time interval thatcomprises the uplink control channel.
 19. The method of claim 1, furthercomprising: identifying a first REG structure associated with a first UEand a second REG structure associated with a second UE; and receiving afirst uplink reference signal from the first UE using the first REGstructure in an RB of the set of RBs.
 20. The method of claim 19,further comprising: receiving a second uplink reference signal from thesecond UE using the second REG structure in another RB of a set of RBs.21. The method of claim 20, wherein the first REG structure and thesecond REG structure differ at least in one of a frequency offset, anumber of REs for reference signals, or a CDM cover code, or acombination thereof.
 22. The method of claim 19, further comprising:receiving data or control information in each RE of an REG associatedwith the first UE in another RB during a second symbol period, the setof REGs comprising the REG associated with the first UE.
 23. Anapparatus for wireless communication, comprising: a processor; memory inelectronic communication with the processor; and instructions stored inthe memory and operable, when executed by the processor, to cause theapparatus to: identify a set of resource element groups (REGs), whereineach REG of the set of REGs comprises a portion of a respective resourceblock (RB) of a set of RBs; map an uplink control channel for a wirelesscommunication link to the set of REGs; and communicate on the uplinkcontrol channel using the set of REGs.
 24. The apparatus of claim 23,further comprising instructions operable to cause the apparatus to:identify an offset associated with a user equipment (UE); and transmitan uplink reference signal using the offset in each RB of the set ofRBs.
 25. The apparatus of claim 23, wherein the set of REGs issemi-statically configured according to an indication communicated usingRRC signaling.
 26. The apparatus of claim 23, wherein the set of REGs isdynamically configured using an indication communicated in a downlinkmessage.
 27. The apparatus of claim 23, wherein a waveform of the uplinkcontrol channel comprises an orthogonal frequency division multiplexing(OFDM) waveform, a discrete Fourier transform spread OFDM (DFT-S-OFDM)waveform, or an interleaved frequency division multiplexing (IFDM)waveform.
 28. The apparatus of claim 23, further comprising instructionsoperable to cause the apparatus to: identify a code divisionmultiplexing (CDM) cover code, wherein communicating over the wirelesscommunication link is based at least in part on the CDM cover code. 29.An apparatus for wireless communication comprising: means foridentifying a set of resource element groups (REGs), wherein each REG ofthe set of REGs comprises a portion of a respective resource block (RB)of a set of RBs; means for mapping an uplink control channel for awireless communication link to the set of REGs; and means forcommunicating on the uplink control channel using the set of REGs.
 30. Anon-transitory computer-readable medium storing code for wirelesscommunication, the code comprising instructions executable to: identifya set of resource element groups (REGs), wherein each REG of the set ofREGs comprises a portion of a respective resource block (RB) of a set ofRBs; map an uplink control channel for a wireless communication link tothe set of REGs; and communicate on the uplink control channel using theset of REGs.